Chemical Control

• Central chemoreceptors

  • Location: medulla
  • Function: monitor the levels of H+, pH, and CO2 in the cerebrospinal fluid (CSF).
• When CO2 levels increase, it leads to an increase in H+ concentration and a decrease in pH, which is detected by the medulla oblongata. In response, the medulla sends signals to the brain to increase the respiratory rate.
• Peripheral chemoreceptors

  • Location: aortic arch and the bifurcation of the common carotid arteries
  • Function: monitor the levels of arterial PaO2, PaCO2, H+, and pH. 
  • These receptors are most sensitive to changes in oxygen levels (detects blood). When oxygen levels decrease, they send signals to the brain to increase respiration.
• Mechanoreceptors (stretch receptors)

  • Location: walls of the bronchi and bronchioles. 
  • During inhalation, the lungs expand, which causes the alveoli to stretch, leading to increased stimulation of these stretch receptors. This triggers the Hering-Breuer reflex, in which the stretch receptors send inhibitory signals to the pneumotaxic area of the pons. The pneumotaxic area then halts further inspiration, preventing excessive inhalation.